System for burning bark



GAS FAN .4l/Q SLOWER l u n' Z;

J. P. BADENHAUSEN SYSTEM FOR BURNING BARK Filed May 1o, 1958 s ,sheets-.sheet 1 S0/LER j,

[um rok com/irak l Jan. 27, 1942.

CONVYR j m .r Mw v v lllll W Jan. 27,1942. J. P. BADENHAUSEN 2,271,157

ssTEM FOR BURNING BARx Filed May l0, 1938 3 Sheets-Sheet 2 Jan. 27, 1942. J. BADENHAUSEN A2,271,157

SYSTEM FOR BURNING BARK Filed May l0, 1958 5 SheetlS-Sheel'l 3 o o u o o oo o a o o u oo f wf f i Patented Jan. 27, 1942 l SYSTEM FOR. BURNING BARK John Phillips Badenhausen, Philadelphia, Pa., assignor of one-half to Day and Zimmerman,

Incorporated, Philadelphia, Pa., a

of Maryland corporation Application May 1o, 193s, serial No..2o7,on6

(Cl. 11o-'1) Y Y showing the main features of the present inven- 7 Claims.

The present invention relates to a,A system for burning bark and more particularly to a`system for preparing the barkfor combustion and for burning in a more effective manner' the combustible constituents of the bark.v y

In the manufacture of pulp and paper the quantities of bark which are obtained are quite large and numerous efforts have heretofore been made to utilize the heat available in the bark.

In the systems heretofore employed the only practical installations which have been available include provisions for pressing the bark to squeeze out the water and thereafter burning the material thus obtained in boilers of the Dutch oventype. In boilers of this type a large re space and grate area is required, the fuel is usually fed in through the furnace roof and it is necessary to provide suitable bridge wallsl and arches in order to obtain combustion.

The size of furnace installation required where 'the Dutch oven type is used is such thatv the cost of such installations is excessive and the combustion and steam generation are not effected as eiiciently as desired. I

It is an object of the' present invention therefore to providea system in which the bark may be suitably prepared prior to combustion and burned in a manner which will increase the heat availablefrom the combustion and increase the eilcierlcy of the heat utilization.

It is a further object of the present invention to provide a system in which the bark, which is vobtained from the rotary barking drums or log barkers of a p'ulp or paper manufacturing plant, is suitably prepared for combustion. k

It is a further `object ofthe present invention to provide a system in which'the preliminary drying of the bark -is effected with waste heat derived from the combustion gases. .v

l It is a further object of the invention to provide a system in which the bark is prepared in such manner that a large area thereof is presented for combustion.

tion;

Fig. 2 isa side elevational view of the stru'cwre shown in Fig. 1;

Fig. 3 is a vertical central sectional view of a form of drier suitable for use in connection with the present invention; Y

Figs. 4 and 5 are plan views of two of. the shelves used in the drier shown in Fig. 3;

Fig. 6 is a Vertical sectional view showing a form of steam generator suitable for use with the present invention; and v Fig. 7 is a detailed fragmentary sectional view showing the structure for introducing the shred-,- ded bark into the steam generator.

It wi1l, of course, be understood that the de-v I scription and drawings herein contained are Vi1- lustrative merely, and that various modifications and changes may be made in the structure `disclosed without departing from the spirit of the invention.

The system in accordance with the present invention is shown more particularly in Figs. 1

' and2 of the drawings. The bark removed from It is a further object of the present invention to provide a system in which the bark is prepared so that the same may be burned in a combustion chamber in suspension.

Other object-s of the invention will appear from the annexed specification and claims.

The nature and characteristic features of the invention will be more readily understood from the following description, taken in connection with the accompanyingdrawings forming part hereof, inwhich:

the logs by the rotary log drums or barkers of the pulp or paper manufacturing plant (not shown) ranges in size from dust to slabs and slashings several feet in length and several inches in width. This material is preferably de? livered from the plant to the system by a suitable conveyor shown diagrammatically at l0 to a discharge chute II by wliich it is .supplied to a drier I2. In the drier I2 the bark is moved downwardly where it is brought into contact during its downward movement with the waste gases of combustion for reducingl the moisture content, as hereinafter 'more fully referred to,

preparatory to further treatment.V

After drying in the'drier I2 the ered to a bark shredder I'3 wherein the bark is shredded as' hereinafter pointed out, and is delivered from the bark shredder I3 by a suitable conveyor Il to a bark storage bin I5. From the bin I5 the shredded bark is delivered into the combustion space I6 of the boiler I1. Preheated air supplied by an air preheater I8 is utilized in part for introducing the shredded bark-into the combustion space IGI; The heat released by the combustion is employed for the generation of steamg. After the combustion of the 4combustible constituents in the combustion space I6 in the boiler I1, the hot gases pass through the air preheater I8, an induced draft fan |79 and a duct 20 to the lower portion of the drier`l2.

A forced draft air blower 2| is provided for bark is delivpreheater I8 to the boiler I1 as hereinafter more fully referred-to.

The drier I2, as illustrated more particularly i in Fig. 3, preferably includes -a cylindrical veri tically disposed outer shell 25 having a duct 26. at the upper end thereof. leading to the .stackv The shell 25 has the intake chute f (not shown). II connected to the upper part thereof for the introduction of the bark brought to 'the system by the conveyor I0. The shell 25 preferably has a `Vertical shaft 21 centrally located therein which is supported at its upper end by a suitable bearing 29 and is preferablyv rotated at-a relatively low speed. A motor 29 and suitable gearing 39 and 3| are provided for driving the shaft 21 at the desired speed.

A plurality of shelves 32 are mounted within the shell 25, the shaft 21 passing downwardly through the center thereof. These shelves 32 are of the character illustrated in Figs. 4 and 5, respectively, each of the shelves 32 having a cutout portion 33 and the cutout portions being each respectively staggered with respect to the cutout portion of the shelf 32 thereabove as indicated in Figs. 4 and 5. 'I'he vertical shaft21 has mounted thereon suitable sweep arms 34 which move the material depositing respectively on the shelves`32 toward the cutout portions 33 so that it may fall in turn to the shelves below, and in falling and downward movement through the drier I2, pass in contact with the upward flow within the shell 25 of the hot gases derived from the combustion space I6.

In-passing from the uppermost shelf 32 to the lowermost'shelf 32 by reason of the agitating movement of the sweeper arms 34, the bark .which initially and upon introduction into the acter of the delivery does not pack or jam eitherl in the throat 35 or in the bark shredder I3.

bark is shredded by the bark shredder I3 which may be of any desired type to a stringy form such that a large area of each separate shredded piece of bark is presented for combustion. The sizeA of the shredded stringypieces of bark obtained from the bark shredder I3 is 4such that the bark may be picked up by the air introduced into the furnace I'I as hereinafter more fully referred to and burned in the furnace- II in suspension in the air stream. 'I'he-bark shredder I3 is .preferably operated by a suitable motor 3B. l The shredded bark from the shredder 'I3 is di-v rected by suitable conveying mechanism shown diagrammatically at I4 and is passed by a chute 31 into the bark storage bin I5 which is preferably arranged directly in front of the boiler I1. The barkbin I5 is provided so that the shredded ,bark may be withdrawn for a controlled feed by means of a plurality of screw conveyors 38 into a downward channel so that the bark falls onto a iloor 39. The shredded bark is picked up by the preheated air flowing through an inlet duct 40 and carried in suspension in the air stream into the combustion space I6 for combustion therein in suspension, as hereinafter pointed out.

The.

practice. The steam generator I1 includes front and rear walls 43 and 44, side walls 45, a top wall 46 and a bottom wall 41. `An upper steam drum 4 8 is mounted in the upper rear part of the steam generator I1, an upper front header 49 is prefer` ably mounted at the junction Vof the front wall 43 and the top wall 46, a `midd1e front header 50 is preferably mounted at a medial location in the front wall 43 and a rear header 5I is preferably mounted at a medial location in the rear wall 44.

Banks of tubes 52 are provided for connecting the upper front header 49 with the steam drum 48 and a' group of tubes 53 -of the bank 52 may line the top wall 46. Banks of tubes 54 are provided for connecting the rear header 5| with the upper front header-49, and banks of tubes 55 which line portions of the inner upper part of the rear wall 44 are provided between the rear header 5I and the steam drum 48. A bank of tubes 56 is preferably also provided for liningr the upper portion of the front wall 43 and extends from the front medial header 50 to the upper front header 49.

-The side walls 45 of the combustion chamber I6 may be provided with suitable Water .tubes as at 51, the tubes 51 on the side walls 45 being connected from a lower side wall header 58 toan upper side wall header 59. The upper side wall header 59 is connected by suitable banks of tubes 60 to the steam drum 48 and the lower side wall header 58 may be connected by suitable banks of tubes 6I and 52 to .the medial front header 50.

Suitable baffles are provided, within the steam generator I1 for directing the gases within the interior thereof in a plurality of passes in heat exchange relation with the banks of tubes 54 and 52. One of these baiiles is shown at 65, along the ,uppermost group of tu'bes of the bank vof tubes`54 and a baille at 55 is provided for directing the gases into contact with the bank of tubes 52 between thev upper front header 49 and the steam drum 48.

An economizer- 58 is preferably providedin the vupper rear portion of the casing of the steam generator I1 and is preferably connected by a suitable bank of tubes 69 to the steam drur 48. The steam drum 48 preferably has steam out-v let pipes 10 which lead to a header 1I of a superheater 12, the superheater tubes being disposed in a pass of the boiler I1. The superheater 12 has a superheater header 13 from which superheated steam is supplied for yuse in the plant.

The air heater I8 is preferably disposed to the rear of the steam generator I1 so that the gases may enter upon their leaving the economizer 58. In Vthe air heater I8 thegases are passed in heat exchange relation with air entering the air heater I8 by a'suitable air inlet 15, the air being supplied to the air inlet 'I5 from the forced draft air blower 2l. The heater air outlet' 16 of the air preheater I8 is connected by a suitable duet 11 to a 'duct 18 communicating with the inlet ductf40.

The hot gases discharged through the gas outlet 19 of the air preheater I8 are drawn by an induced vdraft fan I9 and directed through a. hot gasl duct 20 to the lower portion of the drier I2 where ,they pass upwardly in contact with the bark as heretofore indicated, and pass out through the top of the drier I2 to the stack (not shown).

The front wall 43 of the steam generator I1 is preferably provided with an inlet 89 to which heated -air at a temperature of approximately 556 F. is supplied from the duct 11. A suitable damper 8| is provided for regulating and controlling the quantity of air introduced throughthe inlet 80, so that the air is maintained at substantiallyI constant velocity and there'is no throttlingA by the damper 8|.

The air passing the damper 8l picks up the shredded bark as the same tends to fall to they floor 39 upon its delivery by the conveyors 38, and carries the shredded bark into the combustion space IB of the steam generator l1, the

vvelocity of the air lcurrent being sufficient to effeet the introduction of the shreddedbark.

Upon the entry of the shredded bark into the combustion space IB, because of the relatively small size of the pieces of shredded bark, the same is kept in a suspended condition within the combustion space I8 for and during combustion and presents a relatively large area of each individual piece of shredded bark in contact with the combustion supporting air so that the shredded bark is burned rapidly and the combustible constituents thereof substantially completely burned. Provision is also made for introducing air from the duct 11 through the duct B2 to air inlet openings 83 at the lower portion of the front wall 43 and to suitable tuyres 84 in the bottom wall 41. Air Afrom the duct 82 may also be supplied by the duct 83' connected tothe duct 82 and introduced through air inlets 85 in the rear wall 44.

- The hot gases of combustion as heretofore indicated pass in contact with the banks'of tubes 54 and 52, a substantial part of the heat of the combustion being absorbed by the tubes lining the walls of the combustion space I6 and a substantial quantity of heat` being absorbed by the' other steam generating tubes which are proavailable from the combustion and @within ecof` nomic limits,` is utilized in the economiz'er B8," the preheater 'I8 and the'drier l2.v Iclairnz'. f 1 The method of preparing and burningbark.

which includes'reducing'the moisture content of- 3. The method of preparing and burning bark 'which comprises drying the barkv toreduce the moisture content thereof, then shredding .the

dried bark, and thereafter introducing preheated air and the shredded bark together into a combustlon space, said shredded bark being in suspension 'in said preheated. air, supplying additional separated streams ofl preheated combustion supporting air to said combustion space, burning the shredded bark in the combustion space in suspension, and utilizing the gases of combustion for the initial drying of the bark and forthe preheating of the air. r

4. Apparatus for preparing and burning bark comprising -a furnace. a `bark shredder connected tosaid furnace, a bark drier connected to said bark shredder for drying the bark prior to its yintroductionA into said bark shredder, means for introducing hot gases of combustion from g said furnace into 'said drier for drying the bark passing therethrough to said bark shredder, and means for introducing the shredded fuel mate-l rialinto said furnace for combustion in sus- Densionin said furnace.

5. Apparatus for preparing and burning bark comprising a furnace, a bark shredder connected to said furnace, a drier connected to said bark shredder', means for introducing hot gases of combustion from said furnace to said drier for drying the bark passing therethrough to said shredder, and means for projecting the shredded bark into said furnace, said projecting means including a horizontal plate to which bark is supplied and a duct in communication with said plate for supplying a stream of preheated air for carrying the shredded fuel from said platey into said furnace in suspension. l i 6. Apparatus for preparing andI burning bark comprising a furnace, a bark shredder connected 40A vided. Avlarge proportion of the remaining heat e e e l y y jcom'bustion from saidfurnace to; said drier for 'l dryingthezbark passing` through saiddrii Prior-1 the bark'with a stream of hot gases derived Y from the burningv oflthe bark, preheating airv the bark ofredu'ced moisture content to-a, size such that it may be introduced'and burned in suspension, projecting the shredded bark into a combustion space by a portion of the preheated air, supplying other portions of 'the preheated air to the combustion space at agplrality of locations, and burning the bark in suspension in Vthe combustion space.

. shredded bark in the combustion space and utillzingthe gases of combustion for the initial drying of the bark.

e to .its` "de 1ivery fonco'inbustion therein insuspendedondltibn; f

" said Arnean'sfix ,`1cl`ll1 iiig an yair preheater for supplyingair preheated' by the .hotgases to said :duiven to said furnace, a drier connected to said bark shredder, means for introducinggliot Ygases fof,

to said "Shredders-and means for' furnace and a1 conduit towhichfsaid'preheated with the .same stream of hot gases, shredding 50 `air and said shredded fuel v'are discharged 'fdr A introduction into said'fur'na'fce.

"7. In apparatus for preparing and burning bark, the combination of a bark drier, a bark shredder to which the bark'is ldelivered from a plurality of locations wit and means for delivering /hot furnace gases -to said drier.

Jorn: PHILLIPS BADENHAUSEN. 

